RPM : Speed : Gear Position

. This is a discussion on RPM : Speed : Gear Position within The Technical Zone. Part of The Automotive Answers category; Friends, while taking car from garage, initially at starting RPM shows 1000. After some driving it come below 1000 at ...

+1 and to add to it, if your ac compressor is on , your idle will be higher at that point and will dip once the compressor cuts off. Most modern ECU's also periodically relearn idle - if you hear your car really closely once in a blue moon you might even notice this.

IMO, RPM meter in personal car is just for a reference to the user at what RPM the car engine is running.But RPM has some significant usage for the race car or rally car. Driver has to do some computation with RPM and accordingly need to change the gear or speed . I don't know more on this.
I don't think so, we need to depend on the RPM to change the gear like race car driver do.
If you will see older car, they were not equipped with RPM meter. But now almost all car ,motorcycle comes with RPM meter.I would say this is just a style and your console will look good with some additional gadget.

IMO, RPM meter in personal car is just for a reference to the user at what RPM the car engine is running.But RPM has some significant usage for the race car or rally car. Driver has to do some computation with RPM and accordingly need to change the gear or speed . I don't know more on this.
I don't think so, we need to depend on the RPM to change the gear like race car driver do.
If you will see older car, they were not equipped with RPM meter. But now almost all car ,motorcycle comes with RPM meter.I would say this is just a style and your console will look good with some additional gadget.

Exactly right
RPM meter is mostly for the engine's behaviour. You can monitor the trend is raises at idle and when certain components you turn on. Apart from that some gear head might use it to do optimal gear shift.

RPM meter works in charm if you have a turbo charged or Vtec engine equipped cars. Reason is when you are on the track or road and some random ricer comes along and wants to do a drag.

my skyline's RPM meter I always used for perfect drag shifts in straight line . I used to Redline my R33 to around 7500RPM for every gear. 3rd gear would do 160 at this ratios.

Its advisable to keep the RPM of Diesel engines below 2500
Same way for Petrol engines, it should be kept below 4500.

As per Narayanan Menon from Coimbatore who created a record by achieving a spectacular FE of 42 km per ltr for his Manza, the ideal rpm is 1400.

Any specific reason why petrol engines have an allowed rpm higher than diesels?

My nano's RPM exceed 2500 or so, and I was starting to get worried. I was assuming it as the primary reason for reduced fuel efficiency off late.

Quote:

Originally Posted by autosafari

For a petrol car 3200 RPM at 100 kmph in 5th gear is normal.

Try to keep it around 2800 to 3000.

But in city driving, I think it is impossible to maintain such perfect RPMs. Anytime I see a two-wheeler comes my way, I need to slow and lower the gear. Again in order to maintain momentum and avoid honking from cars behind me, I have to press the gas pedal, thereby, taking the RPM to a higher value.

Instead, always accelerate extremely gradually (imagine that there's an egg placed between the accelerator pedal and the footwell behind it and that you will be shot in the head if you break the egg) and maintaining a constant speed in higher gears (60-70kmph is the best range) for the maximum amount of time. That's what is meant by 'driving with a feather light right foot'.

Great explanation; But, as I said above, very difficult to do so. More so in Nano, I found that the amount of energy to be spent on the acceleration pedal is quite high to make the vehicle catch with the crowd. Of course, lowering from 3rd to 2nd does help and it takes the RPM much above 2500.

To understand the relationship between rpm, speed and gear position, you must understand a few technical terms first. I will try to explain these terms in extremely simple terms:

Sam - Trust me, this is the best and simplest explanation I ever had. Thanks a million for bringing it here. That Cheetah & Elephant example was awesome and can make any dumb to understand the concept clearly.

Quote:

Originally Posted by Sam Dinkar

Let me explain all this in layman terms......

Another killing explanation with simple examples. Hats off!

Quote:

Originally Posted by Sam Dinkar

@sethumurugan: You will never achieve the best fuel efficiency by reaching any rpm range 'as early as possible' -its actually the best way to achieve fuel inefficiency!

Instead, always accelerate extremely gradually (imagine that there's an egg placed between the accelerator pedal and the footwell behind it and that you will be shot in the head if you break the egg) and maintaining a constant speed in higher gears (60-70kmph is the best range) for the maximum amount of time. That's what is meant by 'driving with a feather light right foot'.

Yeah, the Egg thing was funny but very true. I have question on it though.

I drive Figo TDCi and I feel my accelerator is quite sensitive. Means, even a slightest touch makes the car to jerk. So I try to push it even lighter than a feather touch to avoid such jerks and have a comfortable drive. However, when I extend my leg a little more and press the pedal from the center of my foot, the jerk is noticeably lesser. What's wrong or right here?

BTW, I can feel a jerk even while taking the foot off the accelerator.

About the RPM, gear shift & FE - I always have heard, early upshifting is the key to achieve optimum FE. That means, one need to quickly climb the gears and not to revv much. On the other hand, maintaining the power band is also important for optimum FE. So, Aren't these too conflicting? While trying to upshift quickly, we may not reach the powerband (or) to maintain the power band we may either have to delay the gear shift or revv it a little more. Hope you get my question.

PS: In TDCi, Turbo kicks in as early as 1300-1400 RPM and Peak Torque is produced @ 2000 RPM. So if I believe it right, 1500-2000 is the power band.

Last edited by Sam Dinkar; 3rd May 2014 at 09:39 AM.
Reason: Please do not quote long posts unnecessarily. Thanks.

I need your help with this problem I am facing with my Hyundai Verna Fluidic 1.6 SX.

During my 3rd service(@20000 kms) a clutch overhaul was done since the clutch had become quite hard. I know the already existing issue with the clutch cylinder which the Verna models were facing since I had mine replaced a year back.

Since the service representative told me that I would only have to pay for the clutch disc(car is still under warranty) which is quite less compared to the overall procedure(around 15k) I thought why not do it. So the overhaul was done and after that the clutch became quite smooth and I was quite happy with the service till after a few days I started noticing there was something different. My car's gear-rpm-speed ratio has all changed .

What I mean is earlier my car would reach 80kph in 5th gear @1500rpm and now it is only reaching 70kph. For each gear changes like these are observed. My fuel mileage has also come down.

Any advice/suggestion on what could be the reason for this? I have been in and out of the service station 4 times in the last one month complaining regarding this issue and they are saying it is all correct and there is nothing wrong.

Any Verna 1.6 SX owners, could you please tell me how your car's gear-rpm-speed ratios are?
Basically in each gear @1500rpm what the speed is?
Also the idling rpm too?